We know that some spiral galaxies have central bars, and some don't. But do we know why? In this paper, the authors explain some of the factors that influence the creation of spiral bars.Categories: Daily paper summariesTags: galaxies, Hubble sequence, kinematics, morphology, Tully-Fisher relation(Click to read more...)

Classifying galaxies based on their morphology (their shape or form) is a long-standing tradition in astronomy. The most famous classification scheme is that created by the famous astronomer Edwin Hubble: known as the Hubble sequence, it divides galaxies into either spirals or ellipticals, with further distinctions based on how spherical or elongated a galaxy is, or whether the spirals show the presence of a central bar. While classifying galaxies according to their forms can be a fun task in and of itself (check out how many people participate in Galaxy Zoo), characterizing galaxies based on their morphology can also give us clues about how they form and evolve. For example, spiral and elliptical galaxies tend to be found in different environments in the universe – ellipticals are preferentially found in dense regions, whereas almost ...